1. Field of the Invention
The present invention relates to an electromagnetic sound generator, and more particularly to an electromagnetic sound generator that uses sound to indicate the operation of a directional indicator of a vehicle.
2. Description of the Related Art
The mode that is conventionally adopted for operating a directional indicator of a vehicle such as an automobile involves the use of a relay drive. In this mode, a drive current flows and flasher lamps light up each time the relay operates, and the driver can thus be notified of, and can check, the drive and operation of the directional indicator by means of the operation sound.
In addition, Japanese Patent Laid-open No. 14195/98 discloses a vibration generator for notification for a device such as a portable communication device that is used to simultaneously generate vibration and sound to report an incoming call or report the time. FIG. 1 is a vertical section of the vibration generator for notification that is disclosed in Japanese Patent Laid-open No. 14195/98.
Ring-shaped lower yoke 32 and upper yoke 31 are joined by way of magnet 30 inside a case that is made up by lower case 50 and upper case 51; coil 40 and bobbin 41 that constitute first vibrator 11 are inserted in the space between lower yoke 32 and upper yoke 31; and bobbin 41 is joined to disk-shaped second vibrator 21 for generating a notification sound.
Under control from conductor 60, this vibration generator realizes notification by means of vibration caused by the transmission of vibration to cases 50 and 51 that results from first vibrator 11 striking against upper case 51 or lower yoke 32 or by the resilience of spring body 10; and realizes notification by means of sound caused by the transmission of sound waves to the outside from opening 52 that results from the vibration of second vibrator 21.
In recent years, however, the increased functions, miniaturization of control circuits, and higher automobile voltages in compact cars or luxury cars has complicated the adoption of the relay drive mode, which takes up space, in the directional indicator of an automobile, and the demand for the miniaturization of control circuits has brought about the necessity for replacing drive circuits of directional indicators with semiconductor circuits. When using drive circuits that employ semiconductor circuits, however, the driver of a vehicle can be kept aware of the operation of a directional indicator only by means of a visual check of the front instrument panel, and the driver cannot be kept informed by sounds that were conventionally used.
Although the use of a buzzer or speaker can be considered as a means of using sound to keep a driver aware of the operation of a directional indicator, a buzzer emits only sound of a single frequency and thus differs from the operating sound of the prior art and may even be disconcerting to the driver; and although the use of a speaker enables production of a more complex sound, the drive circuit of the speaker may be complicated or the speaker body may be large and therefore entail the problems of increased use of space or higher costs.
In the vibration generator for notification that is disclosed in Japanese Patent Laid-open No. 014195/98, on the other hand, a yoke that is composed of ring-shaped lower yoke 32 and upper yoke 31 and a permanent magnet are provided inside a case composed of lower case 50 and upper case 51, vibrator 21 for generating sound being further provided. This invention therefore entails the problems of complicated construction, and further, difficulty in obtaining a desired sound effect.
It is an object of the present invention to provide an electromagnetic sound generator that can be easily and inexpensively fabricated for generating an indication sound that can be used in vehicles or other environments.
It is another object of the present invention to provide an electromagnetic sound generator that generates sound that is similar to that of a relay of the prior art for keeping the driver of an automobile informed of the operation of a directional indicator, and that can be easily and inexpensively fabricated.
It is yet another object of the present invention to provide an electromagnetic sound generator that can keep the driver informed of the operation of a directional indicator though the use of a sound that does not vary from that of the prior art when the drive circuits of the directional indicator are converted to electronic circuits.
The electromagnetic sound generator of the present invention is made up by: a cup-shaped yoke; a spool on which a coil is wound that can be installed so as to contact the inside of the yoke; a spring having an edge that is secured to the edge of the yoke; a core having its lower surface secured to the central portion of the spring and that is movable up and down as a unit with the central portion of the spring; and a back plate that limits the displacement in the direction of the lower surface of the core; wherein attractive force causes the core to strike the yoke when current is conducted to the coil, and the resilience of the spring causes the core to strike the back plate when current is cut off; thereby producing sound. In addition, the core has a projection for offsetting on its lower surface, and when the spring is secured to the lower surface of the core, the edge of the back plate is secured to the edge of the spring or to the edge of the yoke and the spring is pressed upward by the projection for offsetting of the core, whereby the spring is provided with pretension even without preparatory bending of the spring.
An electromagnetic sound generator according to another aspect of the present invention is made up by: a cup-shaped yoke; a spool on which a coil is wound that is installed so as to contact the inside of the yoke; a spring having an edge that is secured to the edge of the yoke and having at least one protrusion that protrudes from the edge toward the central portion; and a core having its lower surface secured to the central portion of the spring, that can move up and down as a unit with the central portion of the spring, and for which displacement in the direction of the lower surface is limited by the protrusion of the spring; wherein attractive force causes the core to strike the yoke when current is conducted to the coil, and the resilience of the spring causes the core to strike the protrusion of the spring when current is cut off; thereby producing sound.
In addition, each of the above-described inventions may include coil terminals that are secured to the spool on which the coil is wound, that extend from the edges of the yoke and away from the yoke, and that serve the additional role of legs for self-support.
In addition, a single linear slit, a plurality of intersecting slits, or a plurality of slits that extend from the central portion toward the outer circumference may be provided on the upper surface of the yoke; a beam-like portion and lead-like portions that extend in both directions from this beam-like portion may also be provided on the upper surface of the yoke; and further, one or a plurality of vertical slits may also be provided in the side surfaces of the yoke.
The electromagnetic sound generator of the present invention is fabricated by inserting a spool, which is formed as a single unit with coil terminals by pressure-fitting or bonding, into the yoke; and then aligning in the same direction and inserting into the yoke the core and the spring, the core having been subjected to a notching or hole-opening process for preventing contact with the coil terminals that protrude from the yoke; and then welding the back plate to the edge of the yoke by a process such as resistance-welding or laser welding.
More specifically and as shown in FIG. 2 and FIG. 3, the electromagnetic sound generator of the present invention is constituted by: cup-shaped yoke 1 that has been processed by deep drawing; spool 2 on which coil 3 is wound that is installed so as to contact the inside of yoke 1; round spring 5 having an edge welded to the rim of yoke 1 on the open end of yoke 1; core 4 that is welded to the central portion of round spring 5 and that is movable up and down as a unit with-the central portion of round spring 5; coil terminals 6 that are secured to spool 2 on which coil 3 is wound by pressure-fitting or by insert molding and that serve the additional role of support legs for self-support; and back plate 7 that limits the displacement of core 4 in the downward direction; wherein core 4 strikes yoke 1 when current is conducted to coil 3 and core 4 and round spring 5 strike back plate 7 when current is cut off; thereby producing sound. The yoke, which constitutes a magnetic circuit, and the back plate, which limits the free vibration of the core that is attracted and then released, form portions of a case.
A spool on which a coil has been wound, a core that is movable up and down, and a spring are installed inside the cup-shaped yoke, and the conduction and cutting off of current to the coil causes the core to strike the yoke itself or on the spring side to generate a striking sound in accordance with the drive that comes in single beats. The yoke, which constitutes the magnetic drive circuit, also serves as a sound generator, and the provision of openings such as slits in the upper surface and side surfaces of the cup-shaped yoke can enhance sound effects by causing variation in the tone, the sound volume, and the direction of the generated sound.
It is thus possible to generate a sound that resembles that of a relay-type directional indicator of an automobile, and a directional indicator sound for checking operation can be produced that is similar to a conventional indicator despite the use of electronic circuits for the directional indicator.
The above and other objects, features, and advantages of the present invention will become apparent from the following description based on the accompanying drawings, which illustrate an example of a preferred embodiment of the present invention.